The present invention relates generally to fluid seals and apparatus and methods for making them. More particularly, the invention relates to molds adapted to receive and position a rigid seal casing element, normally an annular unit made from metal, and adapted to form contoured annular rubber sections lying along and having at least one surface bonded to such casing, while confining the elastomer to a carefully predetermined area. More specifically, the invention relates to molds having relatively movable elements adapted to embrace a skirt or like portion of an annular stamping element and compress it against an associated but slightly spaced apart counterpart or cooperating mold surface for the purpose of forming a "flash barrier", that is, a barrier against leakage or uncontrolled flow of fluent elastomer which is being formed and then cured in the mold.
With the increasing popularity of so-called "unitized" shaft seals, there has been an increasing need for improved manufacturing methods. By "unitized" as used herein is meant a seal unit wherein two or more relatively movable units, which when combined form a rotary seal, are manufactured, assembled and sold so that there is little or no opportunity for damaging exposure of the sealing surfaces on the seal body and the wear sleeve prior to receipt and installation by the customer. In this way, the manufacturer makes both the elastomeric or resinous sealing element and the associated or wear surface with which it will be engaged in use to form a seal and sells and delivers these units to the manufacturer who installs them on relatively movable parts having opposed cooperating surfaces forming parts of a sealed region.
One feature of such unitized seals is that, as one element, normally the so-called wear sleeve or companion flange is formed, a portion of one of the flanges is made of reduced thickness material to accommodate a subsequent bending or curling operation without damage to the seal. Consequently, as the stamping or other casing element is made, it includes two angularly related flange elements, normally a radial and an axial flange, and at least one of these flanges in turn includes a skirt portion of reduced thickness. In other cases, the skirt thickness is the same as that of the remainder of the casing with the skirt being separated from the remainder of the axial flange by a groove or notch. In still other cases, while not a preferred construction, the skirt is of the same thickness and is merely an extension of the axial flange. In convenience, reference is usually made to the skirt as being of reduced thickness, but this will be understood to refer only to one preferred embodiment and not to constitute an essential feature of the invention.
According to the invention, radially movable parts of the mold engage one surface of this flange, preferably a radially outwardly directed surface thereof, and upon mold closing, move slightly radially inwardly to urge this skirt portion into snug relationship with a radially outwardly directed counterpart or cooperating surface of the mold core. Consequently, an edge or corner of the mold core may engage an opposite surface of the flange at or along its skirt, decreased or reduced thickness portion thereby, to form a secure or tight flash barrier.
The invention includes a mold having a core element, with a portion thereof including surfaces defining part of a mold cavity, a multipart, segmented element resembling a collet or the like surrounding a portion of the core, with each of its elements or segments and having a radially inwardly directed land adapted to engage the skirt, exterior cam surfaces, a cam actuating unit, and one or more additional movable or stationary portions of the mold adapted to define the mold cavity, to locate the casing material or the like. Preferably at least one of these parts includes an additional ridge or land adapted to form another flash barrier with another part of the casing in the closed position of the mold.
Accordingly, in view of the need for improved molding apparatus and method, it is an object of the present invention to provide a mold for manufacturing oil seals or like parts.
Another object of the invention is to provide an oil seal mold which is adapted to position a stamping adapted to have an annular formation of fluent rubber formed therearound and bonded thereto, and to confine the rubber to a predetermined area.
A further object of the invention is to provide a mold unit which includes a fixed core or like element defining a portion of another element for receiving and positioning the stamping, and at least one generally annular cam element adapted to be acted upon when the mold closes to urge a multipart or segmented ring inwardly so as to engage the stamping and urge it against an associated, oppositely directed mold part surface.
Another object of the invention is to provide a mold which is particularly adapted to deform metal temporarily and within its elastic limit for the purpose of forming a flash barrier, but not to deform such metal so as to render it difficult or impossible to remove from the mold after the elastomer is bonded thereof.
Still another object of the invention is to provide a mold apparatus which is able to use existing technology in large part but which can provide further advantages in use.
A still further object of the invention is to provide a mold which includes an annular mold clamping ring having at least one land or rib portion adapted to be compressed or expanded radially so as to elastically deform a portion of a metal casing therein, which ring is subdivided into plural parts and urged into a spaced apart position from the work to be engaged by an annular spring and which is adapted to be moved oppositely by a cam element, with the two parts having mutually engageable cam surfaces. Another object is to provide a mold which can conveniently provide both radial and axial barriers in the same unit.
Another object of the invention is to provide a method of forming an annular bead of elastomer and bonding it to a metal or like rigid casing which includes positioning a stamping having a portion exposed to and forming one surface of a mold cavity, engaging another part with a radially movable mold element so as to urge a portion of the casing snugly against a mold part lying just opposite the first part and separated therefrom by the thickness of the casing material, and closing the mold and forming a second flash barrier by engaging the spaced apart portion of the casing with a flash barrier land and while maintaining the rib in snug engagement with the stamping skirt, filling the mold with fluent rubber and permitting it to bond to the casing surface before releasing the encircling forces on the skirt, and then opening the mold for release of the completed product.
The foregoing and other objects of the invention are achieved in practice by providing a mold having a core section and a stamping support and positioning section which includes both radially immovable and movable parts, with the movable part including a skirt-engaging land portion and consisting of plural segments adapted to be urged radially by a cam action into engagement between the rib and the skirt, and means for holding the mold in the closed position while fluent rubber is forced into the mold cavity formed in part by mold element surfaces and in part by the casing received in the mold.
The invention also achieves its objects by providing a molding method which includes positioning a stamping having an axial flange with a marginal skirt portion and transiently radially deforming the skirt portion during the time a fluent elastomer is forced into bonding relation with another portion of the casing, maintaining the flash barrier until the elastomer has at least partially cured, and thereafter opening the mold to remove the finished part.
The exact manner in which the foregoing and other objects and advantages of the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings in which like reference numbers indicate corresponding parts throughout.